Silvia Vettore

Arterial and venous thrombosis in rare congenital bleeding disorders: a critical review

Summary.  A thorough review of the literature and of personal files has allowed the gathering of 81 patients with rare congenital bleeding disorders and thrombotic phenomena. Sixteen of these patients had congenital afibrinogenemia, eight involved factor V deficiency, 20 factor VII defects, 33 factor XI deficiencies and only one, a factor XIII defect. Altogether 42 patients showed arterial thrombosis (myocardial infarction [MI] in 28 cases; ischemic stroke in 4; arterial occlusion in 8; 2 patients with disseminated intravascular coagulation (DIC)). Ages varied between 13 and 74. Twenty‐two patients were males and 16 females. In four cases, sex was not reported. There were three fatalities: two after a MI and one because of heart failure. With regard to venous thrombosis: 9 patients had pulmonary embolism, 15 patients had deep vein thrombosis, 9 patients had both pulmonary embolism and deep vein thrombosis; 1 patient had superficial vein thrombosis, whereas, 5 cases had an unusual site venous thrombosis (two portal systems, two cerebral sinuses, one inferior vena cava) for a total of 39 cases. Age varied between 3 and 86. In this case, 20 patients were males and 17 were females. In two cases, sex was not reported. There were three fatalities: two because of pulmonary embolism and one because of inferior vena cava thrombosis. The fact that thrombosis has never been described in patients with factor II or factor X seems to underscore the central antithrombotic role that these two factors have in the coagulation system.

Novel point mutation in a leucine-rich repeat of the GPIbα chain of the platelet von Willebrand factor receptor, GPIb/IX/V, resulting in an inherited dominant form of Bernard-Soulier syndrome affecting two unrelated families: the N41H variant

This reports describes a new variant of heterozygous Bernard-Soulier syndrome with autosomal dominant inheritance. In Italy, a significant proportion of patients with autosomal dominant inheritance of macrothrombocytopenia have been recognized as having heterozygous Bernard-Soulier syndrome carrying the Bolzano-type defect. This condition prompted a systematic review of our out-patients with chronic isolated macrothrombocytopenia. We recognized that the affected members of two unrelated families represented a new variant of heterozygous Bernard-Soulier Syndrome with autosomal dominant inheritance. Sequencing analysis of the GPIbα gene revealed a novel heterozygous mutation, A169C, resulting in an N41H substitution in the protein. This aminoacid belongs to the first leucine-rich repeat of the chain. The molecular modeling suggests that the replacement of the N41 with a histidine (N41H) drastically disturbs the structure of the first portion of GPIbα N-terminal, directly involved in von Willebrand factor binding. As a consequence, platelet aggregation to 1.2 mg/mL of ristocetin is slightly impaired and flow cytometry reveals a reduced binding of monoclonals directed against N-terminal epitopes of the GPIbα.

Determinants of Plasma Levels of Plasminogen Activator Inhibitor-1: A Study of Normotensive Twins

We investigated whether plasma levels of the plasminogen activator inhibitor type 1 antigen (PAI-1:Ag) are genetically determined in monozygotic (MZ) and dizygotic (DZ) twins. Twenty-five pairs of healthy twins underwent measurements of PAI-1:Ag and other variables, including body mass index, mean blood pressure, plasma renin activity, insulin, and glucose. To ascertain the zygosity of twins, highly discriminating micro- and minisatellite systems with variable numbers of tandem repeats were analyzed by PCR amplification followed by polyacrylamide gel electrophoresis. Subjects were also genotyped for the 4G/5G polymorphism by PCR. Estimates of genetic variance and heritability were obtained for PAI-1:Ag, and for body mass index, mean blood pressure, plasma renin activity, glucose, and insulin by jointly examining data in a path analysis with TWINAN90. Results showed that 12 pairs of twins were MZ and 13 were DZ. All tests of genetic variance [within pair (WP): F=6.24, P=0.002; among component (AC): F=2.62, P=0.04; average absolute difference t test=3. 00, P=0.004] showed significant genetic variance of PAI-1:Ag, but not of the other variables. Three tests of heritability (WP=0.837, P=0.002; AC=1.791, P<0.05; intraclass correlation: 1.180, P=0.001) consistently showed significant PAI-1:Ag heritability. Additive genetic influences (A), dominance genetic effect (D), and random environmental influences (E) accounted for 0.714, 0.154, and 0.132 of PAI-1:Ag variance, respectively. No effect of different 4G/5G genotypes was found. Thus, these results show significant genetic variance and heritability of PAI-1:Ag and suggest that A is more important than both D and E in determining PAI-1:Ag variance.

Associated prothrombotic conditions are probably responsible for the occurrence of thrombosis in almost all patients with congenital FVII deficiency. Critical review of the literature

The occasional occurrence of thrombosis in patients with congenital bleeding disorders has received considerable attention during the past decade. Myocardial infarction, ischemic strokes and venous thromboembolism have been reported in hemophilia A or B patients, in von Willebrand disease and, also, in rare coagulation disorders, especially in factor VII (FVII) deficiency. To explain the relatively high frequency of thrombotic phenomena, mainly venous, seen in the last condition, it was speculated that a special form or variant of FVII deficiency could exist. The presence of associated prothrombotic risk factors has been occasionally reported to be present in these patients but the matter has never been duly evaluated and emphasized. The purpose of the present paper was to evaluate if the clinical setting in which thrombosis appeared in these patients could explain the occurrence of the thrombosis. All reported cases of thrombosis seen in patients with FVII deficiency have been analyzed and the presence of associated risk factors recorded. Out of a population of 33 documented cases, the presence of prothrombotic risk factors was reported in 30 instances. In two of the remaining cases, no mention is made about associated risk factors. In the last case they were explicitly excluded. The critical evaluation of the literature suggests that the occurrence of thrombosis in FVII deficiency may be due to common prothrombotic risk factors. As a consequence it may be only stated that FVII deficiency does not protect from thrombosis.

Arterial and venous thrombosis in patients with von Willebrand’s disease: A critical review of the literature

All patients with von Willebrand’s disease (vWD) who showed an arterial or venous thrombosis and were reported in the literature have been evaluated. 11 patients had arterial thrombosis while 19 had venous thrombosis for a total of 30 cases. 9 out the 11 cases with arterial thrombosis had myocardial infarction. Two had cerebral thrombosis. Associated risk factors for arterial thrombosis were available only for three patients who showed, respectively, smoking and dyslipidemia (2 cases) and smoking and intravenous desmopressin infusion (1 case). The majority of patients with venous thrombosis showed DVT with or without PE. Four patients presented with apparently isolated PE. In two instances thrombosis occurred in unusual sites (central retinal vein and portal vein, respectively). Several associated risk factors were present, mainly: infusion of FVIII or FVIII + vWF concentrates in 7 cases; surgery in 8 cases, pregnancy in 1, desmopressin infusion in 1, variable coagulation defects or polymorphisms in 5. More than one of these associated conditions were present in a few patients. The majority of vWD patients who showed thrombotic phenomena were type I patient, but in 6 cases were also type 3. The type of defect was not reported in 6 patients. As a conclusion of this review it seems safe to assume that both arterial and venous thrombosis appear rare in vWD. This is confirmed by the fact that arterial or venous thrombosis appears slightly more frequent in hemophilia A and B.

Molecular and cellular diversity of heart conduction system myocytes

Conduction system myocytes are a subpopulation of cardiac myocytes that display unique electrophysiologic properties. Significant differences in cellular components of conduction myocytes have been demonstrated by the application of in situ procedures using both immunologic and molecular probes. Although molecular and cellular biology investigations are still at the beginning, they unequivocally show that conduction myocytes are a highly heterogeneous myocyte population, whose difference from working myocytes might reflect both the degree of functional specialization and the origin from a cell lineage distinct from myocardial cells.

Impairment of fibrinolytic potential in long-term steroid treatment after heart transplantation.

Thrombotic complications constitute an important risk in transplant recipients, in whom a hypercoagulable state and hypofibrinolysis have been associated with immunosuppressive treatment, especially with cyclosporine. In no case have clotting and fibrinolytic abnormalities been correlated with steroid immunosuppression, even though steroids were always administered. Previous studies found a relationship between hypercorticism and hypofibrinolysis both in Cushings disease and after renal transplantation. The aim of this investigation was to compare fibrinolytic potential using the venous occlusion test in two similar groups of heart transplant patients treated with or without steroids. Euglobulin lysis time, tissue-type plasminogen activator and plasminogen activator inhibitor-1 (PAI-1) activities, and antigens were determined before and after the venous occlusion test. A reduced fibrinolytic potential (significant prolongation of lysis time) due to a significant increase in PAI-1 activity and antigen levels was found in heart transplant patients treated with steroids, as compared with patients without steroid treatment and control subjects. The prevalence of reduced fibrinolytic potential was 69.2% (18 cases) in the steroid-treated group and 34.8% (8 cases) in the non-steroid-treated group. In every case, the impaired fibrinolytic potential was due to high basal PAI-1 levels. Our results are compatible with the presence of a hypofibrinolytic state secondary to long-term steroid treatment. In heart transplant recipients, steroid-induced hypofibrinolysis may constitute a further risk factor for thrombotic disease.

Congenital FVII deficiency and thrombotic events after replacement therapy

Thrombosis has been occasionally described in congenital FVII deficiency. This report deals with patients with FVII deficiency who presented thrombotic events after substitution therapy. At least 12 patients are reported in the literature. In all but two cases thrombosis occurred after prothrombin complex concentrates or plasma derived FVII concentrates. In two instances pulmonary embolism occurred after the administration of large amounts of whole blood. Concomitant prothrombotic risk factors were present in most of these cases (surgery, immobilization, old age, etc.). Personal files allowed us to add another patient who developed bilateral pulmonary embolism after two vials of an aFVII concentrate. In this case also, concomitant risk factors were present, namely surgery for hysterectomy, immobilization. The pulmonary embolism occurred in spite of the congenital FVII deficiency indicating that no sure antithrombotic protection is assured by this defect. The actual needs of substitution therapy in patients with some variants of FVII deficiency is discussed, together with comments on the therapeutic management of the thrombotic events in these patients.

Platelet response to Helicobacter pylori eradication therapy in adult chronic idiopathic thrombocytopenic purpura seems to be related to the presence of anticytotoxin-associated gene A antibodies

The aims of this study were to assess the prevalence of Helicobacter pylori infection in chronic idiopathic thrombocytopenic purpura adult patients and investigate the platelet response after eradication. To minimize the confounding effect of concomitant idiopathic thrombocytopenic purpura therapies, patients were eligible for the prospective study if they had 20–100 × 109/l platelets, and no requirement for treatment for thrombocytopenia or no change of doses of ongoing medications for at 3 months before inclusion.Helicobacter pylori infection was assessed in 62 patients using a stool antigen test, and the infection was present in 52% of patients. Immunoglobulin G antibodies against the cytotoxin-associated gene A protein were detected in 53% of infected patients. All patients underwent sampling for specific platelet autoantibodies, 37.5% of H. pylori-positive and 33% of H. pylori-negative patients had detectable platelet autoantibodies. Sixteen eligible H. pylori-positive patients were submitted to the eradication therapy and followed in the prospective study. We considered 14 H. pylori-negative patients as control group. Platelet response was defined as an incremental increase above 50% from baseline platelet count. A positive response was observed in 43% patients after 6 months of follow-up. Eradicated responder and nonresponder patients were comparable for all main clinical features but not for anticytotoxin-associated gene A antibodies (83 vs. 12.5%, P = 0.026).Given the good cost–benefit ratio, we believe that all idiopathic thrombocytopenic purpura patients should be screened for H. pylori infection and eradication treatment should be considered, particularly for patients who are also found positive for anticytotoxin-associated gene A antibodies.

The clinical significance of the lack of arterial or venous thrombosis in patients with congenital prothrombin or FX deficiency

Several reports have dealt with the occurrence of both arterial and venous thrombosis in patients with haemophilia A, haemophilia B, and von Willebrand disease. Similar thrombotic events have been occasionally reported also in rare congenital coagulation disorders, particularly in fibrinogen or FVII deficiencies. On the contrary no sure venous or arterial thrombotic event has ever been reported in congenital prothrombin or Factor X deficiency. The significance of this observation is discussed. This discrepancy cannot be explained on the basis of the rarity of the two conditions, since in similarly rare congenital bleeding disorders such as FV or FXIII deficiency a few patients with thrombosis have been described. It appears that only these two defects are able to allow a sure protection from thrombosis. These observations may indirectly support the rationale for the use of direct thrombin or Factor X inhibitors in the prophylaxis and/or therapy of thrombotic manifestations.